Physical Properties

• What are the 3 types of bonding ?

  Ionic, Covalent and Metalic
• What are the 2 types of structures ?

  Giant and simple
• What are the 4 types of structure and bonding ?

  1. Giant Ionic
  2. Giant Metallic
  3. Giant Covalent
  4. Simple Covalent
• In a solid state, what do ionic compounds exist as ?

  Giant Ionic Lattices
• Describe the melting and boiling points of a Giant Ionic Lattice.


  Giant ionic lattices have a high melting and boilling point and are always solid at RTP because they have a network of strong ionic bonds which require large amounts of energy to break.
• Describe the solubility of Giant Ionic Lattices.

  Giant ionic lattices are usually soluble in polar solvents e.g. H2O because the water molecules can break up the lattice, and surround the ions to form a solution.
• Describe the electrical conductivity of Giant Ionic Lattices.

  In a solid state, giant ionic lattices do not conduct electricity as the ions are fixed in place and cannot move. However they can conduct electricity in a molten state or in aqueous solution because they have mobile ions.
• Define metallic bonding.

  The electrostatic force of attraction between positive metal ions and delocalised electrons.
• Describe the physical properties of metal compounds. (conductivity, mp and bp )

  Conductivity :

  Metals are good conductors of electricity because the delocalised electrons can move through the lattice.

  Melting/Boiling Point:

  The electrostatic force of attraction between delocalised electrons and the positive metal ions are strong. This causes metals to have high melting and boiling points.
• Which metal is liquid at RTP ?

  Mercury
• What does allotrope mean ?

  Different forms of the same element.
• Name are the allotropes of carbon ?

  Diamond, graphite, graphene
• What is the shape around the carbon of diamond ?

  Tetrahedral
• What is the shape around the carbon of Graphite ?

  Trigonal Planar
• What are 3 differences between Diamond and Graphite ?

  1. In diamond each carbon is covalently bonded to 4 other carbons to make a tetrahedral structure. But in graphite each carbon is covalently bonded to 3 other carbons to make a trigonal planar.
  2. Graphite has delocalised electrons which are free to move and found between the layers.
  3. Graphite is layered
• Describe and explain the melting points of Diamond and Graphite.

  Diamond :

  Diamond has a high melting point. This is because of the strong covalent bonds between carbons and the giant structure. This means that high temperatures are required to break bonds.

  Graphite :

  Graphite has a high melting point. This is because of the strong covalent bonds between carbons and the giant structure. This means that high temperatures are required to break bonds.
• Describe and explain the difference in electrical conductivity between Diamond and Graphite.

  Diamond :

  Diamond does not conduct electricity. This is because all 4 electrons are used in bonding. There are no mobile ions or delocalised electrons.

  Graphite :

  Graphite does conduct electricity. This is because 3 electrons are used in bonding but one is delocalised between the layers. The delocalised electons are free to move and carry charge.
• Describe and explain the solubility of Diamond and Graphite.

  Diamond:

  Low solubility. Insoluble in almost all solvents. Solvent cannot break apart lattice of strong covalent bonds.

  Graphite:

  Low solubility. Insoluble in almost all solvents. Solvent cannot break apart lattice of strong covalent bonds.
• Describe the structure and bonding of Silicon.


  Silicon is similar to Diamond. Silicon makes 4 bonds with other silicon atoms, creating 4 covalent bonds. This gives silicon a tetrahedral structure. This makes the melting and boiling point really high.
• What is graphene ?

  a single layer of graphite
• What element has the same electrical conductivity as graphene ?

  copper
• Describe the m.p and b.p of graphene.

  High m.p and b.p because there are strong covalent bonds between the carbons.
• Describe the Electrical conductivity of graphene.


  Graphene does conduct electricity because the carbon atoms only make 3 bonds so the fourth electron is delocalised, free to move.
• Describe the strength of Graphene.

  Very strong because the carbons are arranged in a hexagonal shape bonded by strong covalent bonds.
• What is the weakest intermolecular force ?

  London Forces
• What is the strongest intermolecular force ?

  Hydrogen bonding
• Covalent molecules are held together by which intermolecular forces ?

  Hydrogen Bonding, London forces, Permanent dipole dipole
• Describe the bonding in I2 (iodine).


  Within each I2 molecules the iodine atoms are held together by strong covalent bonds. The I2 molecules are held together by weak London forces in a regular 3 dimensional lattices.
• Describe the bonding in H2O.


  Within each H2O molecule the O and the H are held together by strong covalent bonds. The H2O molecules are held together by hydrogen bonds between the molecules.
• Describe the trend between London forces and number of electrons.

  Increasing the number of electrons means larger induced dipoles. This increases the strength of London forces between molecules. Therefore boiling point increases.
• Explain the trend in boiling point for G17.


  As you go down group 17, the number of electrons increases, larger induced dipoles and strength of London forces between molecules increases. These forces will require more energy to overcomes so the oiling point increases.
• Do simple molecular structures conduct electricity?

  No, there are no mobile ions or delocalised electrons.
• What do non polar, simple molecular structures dissolve in ?


  Non polar solvents such as hexane
• Why is ice less dense than liquid water?


  When water freezes into ice, a network of hydrogen bonds for. The H2O molecules are held apart in an open lattice structure. There is lots of space in the structure which gives ice a lower density than water. When ice melts hydrogen bonds break which allows the liquid H2O molecules to move closer together.
• Why does water have a relatively high melting and boiling point compared to similar molecules ?


  Hydrogen bonds are extra forces, on top of London forces. When ice melted or water boiled, these strong Hydrogen bonds need to be broken. More energy is needed to do this than for other molecules which do not possess hydrogen bonding.